drought tolerance through biotechnology: improving translation from the laboratory to farmers’...

Drought tolerance through biotechnology: improving translationfrom the laboratory to farmers’ fieldsJill Deikman1, Marie Petracek2 and Jacqueline E Heard3

Available online at www.sciencedirect.com

Water availability is a significant constraint to crop production,

and increasing drought tolerance of crops is one step to gaining

greater yield stability. Excellent progress has been made using

models to identify pathways and genes that can be

manipulated through biotechnology to improve drought

tolerance. A current focus is on translation of results from

models in controlled environments to crops in the field. Field

testing to demonstrate improved yields under water-limiting

conditions is challenging and expensive. More extensive

phenotyping of transgenic lines in the greenhouse may

contribute to improved predictions about field performance. It

is possible that multiple mechanisms of drought tolerance may

be needed to provide benefit across the diversity of water

stress environments relevant to economic yield.

Addresses1 Monsanto Company, 1920 Fifth Street, Davis, CA 95616, United States2 Monsanto Company, 700 Chesterfield Parkway West, Chesterfield, MO

63017, United States3 Monsanto Company, 25 First Street, Suite 404, Cambridge, MA 02141,

United States

Corresponding author: Heard, Jacqueline E

([email protected])

Current Opinion in Biotechnology 2012, 23:243–250

This review comes from a themed issue on

Plant biotechnology

Edited by Dianna Bowles and Stephen Long

Available online 9th December 2011

0958-1669/$ – see front matter

Published by Elsevier Ltd.

DOI 10.1016/j.copbio.2011.11.003

IntroductionWith the rising global population, increasing crop yield is

the fundamental challenge for the agricultural industry.

Considerable progress in improving agricultural pro-

ductivity has been made over the last 50 years. With a

single acre of land, a farmer in the US today can produce

the equivalent of enough food for 151 people, more

than twice the production of 1960 (http://www.usda.gov/

documents/Briefing_on_the_Status_of_Rural_America_

Low_Res_Cover_update_map.pdf). Can we maintain or

improve that trend in order to feed the 2 billion additional

people that will live on this planet by 2050 [1]? In

addition, climate change is expected to negatively impact

crop production because of variable temperatures and

more frequent drought in many parts of the world by

www.sciencedirect.com

the middle of the 21st century [2], making development

of varieties that can yield well under harsh environments

even more critical for the prevention of food shortages. It

is estimated that yield potential for maize is about 3-times

current commercial yields, and much of the gains over the

last few decades has come from improving stress toler-

ance, which remains a promising trait for further optim-

ization [3].

Insufficient water is one of the most important limitations

to plant growth and crop yield [4,5�]. A simple definition for

drought in the context of agriculture is any situation when

the amount of water available to the plant is less than what

is required to sustain maximum growth and productivity.

Breeders have made excellent progress improving crop

phenology, such as flowering time, height and other traits

that can affect water utilization through avoidance strat-

egies [6], but it is clear that additional improvements are

required to make the needed step-change in crop pro-

ductivity during periodic and/or sustained periods of

drought stress that are commonly experienced in rain-

fed agriculture, or when irrigation is limiting. These

improvements may be achieved through breeding, through

biotechnology, or a combination of the two.

The first generations of biotechnology traits were devel-

oped to control insects and weeds, and they provide

improved yield protection while reducing the amount

and cost of chemical inputs. Economic benefits to farmers

are clear and have driven adoption of this technology at an

impressive rate [7,8��].

Plants use multiple strategies to respond to drought

stress, so there are many candidate pathways to engineer

to enhance stress tolerance. Plants may escape stress by

accelerating flowering before onset of severe drought [9].

Alternatively, they may cope with stress by reducing

water use by slowing growth, closing stomates and

increasing impermeability of cuticles [5�,10�], or improv-

ing water acquisition by increasing root development

[11]. Plants also have mechanisms to tolerate drought,

such as osmotic adjustment, and production of antiox-

idants [12]. The plant hormone abscisic acid (ABA) is

synthesized in response to drought stress and coordinates

many of these strategies to protect plants from desiccation

[13]. Adding to the complexity, drought can occur at

different times during the growing season, and crops

respond quite differently to drought stress depending

on developmental stage. For example, water deficit has

the greatest negative impact on maize yields when

experienced during flowering [14,15]. Drought is rarely


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http://www.sciencedirect.com/science/journal/09581669

244 Plant biotechnology

experienced in isolation, but may be accompanied by heat

and/or nutrient stress. Yield is ultimately determined by a

complex set of interacting response pathways that can

vary across germplasm. Finally, most agricultural appli-

cations require development of varieties with improved

yield under drought that also yield competitively under

optimal growing conditions. However, many of the mech-

anisms for water conservation in plants cannot be

exploited owing to a trade-off with yield performance

in the absence of stress [5�,10�].

Agriculture companies have already spent decades devel-

oping drought tolerant crops. Maize hybrids with improved

drought tolerance currently on the market have been

developed using conventional breeding [16]. A first-gener-

ation product developed using biotechnology is targeted

for the water-limited western U.S. corn-belt, and will be

tested on commercial farms in 2012, pending additional

approvals by regulatory agencies (http://www.monsanto.

com/products/Pages/drought-tolerant-corn.aspx). This

new product represents just the beginning of the potential

for improving drought tolerance in crops. A portfolio of

products is in development by various companies using

biotechnology to improve yields further under stress and/or

to provide tolerance under a greater variety of drought

stress profiles or growing regions for maize and other

species.

Work to engineer stress tolerance in crops has been

reviewed previously [12,17�]. This review will highlight

Figure 1

Testing in crops in growthchamber or greenhouse

Identification ofgene lead in models

High throughput p

pr

predict

Typical process for development of drought tolerant crop using biotechnolog

use of high throughput phenotype analysis for optimization of crop phenoty


the most advanced biotechnology traits, and also new

candidates reported in the last 3 years with demonstrated

stress tolerance in crops. Strategies for moving from

demonstration of drought tolerance in a controlled

environment to development of drought tolerant crops

will be discussed (Figure 1).

Progress on gene to trait translationThe impact of the age of genomics is just beginning to be

realized for crop improvement. The Arabidopsis genetic

model has allowed the identification of numerous path-

ways important to growth under limiting water [12,18],

and these pathways tend to be conserved among species

[19]. In the last decade, one of the most promising break-

throughs in basic scientific research has been in under-

standing ABA biosynthesis, ABA receptors, and other

components of the ABA signal transduction pathway

[20��,21]. This valuable new mechanistic understanding

of the complex ABA signaling pathway should expedite

innovations around managing plant responses to drought.

Biotechnological approaches to improve drought stress

tolerance in plants may involve overexpression of genes

involved in particular aspects of cellular homeostasis such

as osmotic adjustment, chaperones, or antioxidants

[12,17�]. Alternatively, ectopic expression or suppression

of regulatory genes could potentially activate multiple

mechanisms of stress tolerance simultaneously [22].

Genes encoding members of the AP2/ERF transcription

factor family including the Dehydration Responsive

Genediscovery

Commercialdrought tolerant

product

Field testing foryield +/- drought

henotyping

edict

inform

inform

Current Opinion in Biotechnology

y. Traditional process is indicated by blue arrows. Green arrows indicate

pes.


http://www.monsanto.com/products/Pages/drought-tolerant-corn.aspx

http://www.monsanto.com/products/Pages/drought-tolerant-corn.aspx

Drought tolerance through biotechnology Deikman, Petracek and Heard 245

Element Binding Proteins [23], ABA Response Element

Binding Proteins, and NAC transcription factors [19] have

all shown promise, as well as genes encoding proteins

involved in other aspects of signal transduction, such as

kinases and protein modification enzymes [17�]. In

addition, progress in identification of plant microRNAs,

including those with expression altered by drought stress

[24–28], provides exciting new targets for controlling

drought response pathways.

Demonstration of drought stress tolerance in crops in

controlled environments is proceeding at an encouraging

rate (Table 1; [17�]). Many of these recent discoveries

have been in rice, which is both an excellent model

species for basic research, and one of the world’s most

important crops. Study of rice mutants with altered stress

tolerance led to the identification of genes in three path-

ways that can be manipulated to improve stress tolerance

[29,30��,31]. Several genes that can provide drought stress

tolerance were identified by altered expression of genes

shown to be induced by drought stress in rice [32–35,36��,37��,38��,39]. Findings from Arabidopsis continue

to be a rich source of drought leads [40–50]. Some

transgenes were derived from extremely stress-tolerant

species such as Thellungiella halophila [51], a salt-tolerant

relative of Arabidopsis, and Atriplex hortensis [52], although

direct comparison of alleles from less tolerant species is

needed to validate this approach. Overexpression of some

regulatory proteins has led to dwarf phenotypes with

reduced yields, but use of drought-inducible [23,53] or

tissue-specific [54] promoters may overcome this issue.

The magnitude and consistency of gene effects may be

improved by co-expression of 2 or more transgenes that

each provide drought efficacy, ideally through different

mechanisms [55].

Improving trait to yield translationMany genes have been identified that can improve

drought tolerance (Tables 1 and 2, [17�]), but progress

towards commercialization of these traits has been slow.

Demonstration of drought efficacy in the field is a critical

step for showing commercially relevant drought toler-

ance, but resources for this testing are limited for many

researchers, and governmental regulation of transgenic

crops is often a barrier to field testing [56].

Benefit from several transgenes has been demonstrated in

field trials. One example is the Cold Shock Protein B

(CspB) RNA chaperone from Bacillus subtilis. CspB plays

a role in adaptation of bacteria to low temperatures, and its

overexpression was shown to provide stress tolerance to

Arabidopsis, rice and maize [57]. Results from field testing

at multiple locations with controlled irrigation showed that

maize lines expressing the CspB gene had higher yield

under water-limiting conditions than controls, and also had

yields equivalent to controls under optimal growing con-

ditions. While this transgene provided significant yield


improvements, it is expected that the addition of trans-

genes with different modes of action can complement the

performance of this gene, and may expand the geographic

regions and growing conditions under which benefit may

be obtained.

Table 2 contains several other recent examples in which

transgenic lines have demonstrated improved drought

tolerance in field testing. In one experiment, 7 transgenes

with ability to improve stress tolerance in model species

were tested in transgenic rice in field trials over two years

[53]. Each gene was tested with 2 promoters, one con-

stitutively expressed and the other drought-responsive.

Efficacy in promoting drought tolerance was demon-

strated for 6 of these genes with one or both promoters.

This experiment provides an excellent example of fairly

rapid movement of transgenes with known efficacy from

models into crops, and it is hoped that some of these

genes will ultimately have commercial utility.

An example that demonstrates the importance of testing

the translation of greenhouse experiments to field per-

formance was reported for the AP37 and AP59 genes in

rice [58]. Overexpression of these genes in transgenic rice

showed that either gene improved drought tolerance

phenotypes in the growth chamber, but only AP37

showed yield improvement under drought in the field.

One phenotype that may lead to a difference in green-

house and field results is reduced plant size. Smaller

plants use less water and thus have more water available

compared to larger control plants in identical pots. How-

ever, in the field this mode-of-action may not give benefit,

and may even produce yield drag [59]. Testing drought

tolerance in field trials is difficult, even if controlled

irrigation is available, because of the unpredictable varia-

bility of weather, soil, rain, and pests or diseases. Further-

more, some transgenes may function in pathways that

interact with environmental parameters, leading to vari-

able results. The conceptually simplest way to deal with

these issues is to test at many locations over multiple

years. However, this kind of testing is expensive and

time-consuming.

More thorough characterization of transgenic lines may

improve the ability to predict which lines are likely to

show benefit in field conditions. This characterization

may be enhanced by use of high-throughput phenotyping

methods, which are often based on non-destructive ima-

ging techniques to quantify biomass, shoot architecture,

photosynthesis, pigmentation, water content, transpira-

tion rate, and other traits [60��,61,62]. High-throughput

methods for imaging root architecture have been devel-

oped [63], creating opportunities to generate a more

complete phenotypic profile. Field performance data

from transgenic plants can be combined with thorough

phenotypic data obtained in a greenhouse, using different

stresses and taken at a variety of developmental stages, to



Table 1

Transgenic improvement of drought tolerance demonstrated in pots in crops from 2009 to mid-2011. These references include

experiments conducted in growth chambers, greenhouse, or in pots outdoors. Ah, Atriplex hortensis; Ca, Capsicum annuum; Gh,

Gossypium hirsutum; Gm, Glycine max; Hv, Hordeum vulgare; Os, Oryza sativa; Ta, Triticum aestivum; Ts, Thellungiella halophila.

Pathway Gene family Gene Discovery strategy Transgenic expression Crop Reference

Osmoregulation H+-PPase TsVP hypothesis CaMV35S cotton [51]

AVP1 hypothesis CaMV35S alfalfa [66]

betaine aldehyde

dehydrogenase

AhBADH hypothesis Zm.Ubiquitin wheat [52]

choline

dehydrogenase

betA hypothesis Zm.Ubiquitin wheat [67]

detoxification Glutathione S

transferases

GsGST hypothesis CaMV35S tobacco [68]

ABA response AREB bZIP OsbZIP72 Arabidopsis CaMV35S rice [40]

GmbZIP1 Arabidopsis tobacco: 35S and rd29A

(drought); wheat: ubiquitin

tobacco

and

wheat

[41]

SlAREB reverse genetics in tomato

of stress induced gene

CaMV35S tomato [69]

ABA synthesis beta-Carotene

Hydroxylase

OsDSM2 rice mutant CaMV35S rice [29]

farnesyltransferase/

ABA sensing?

farnesyltransferase/

squalene synthase

SQS hypothesis RNAi rice [70]

disease response;

ABA

Harpin hrf1 hypothesis CaMV35S rice [71]

stomatal regulation DST OsDST rice mutant RNAi rice [30��]

stress response AP2/ERF TsCBF1 Arabidopsis/halophyte

gene source

Zm.Ubiquitin maize [44]

JERF1 Arabidopsis / ABA induced CaMV35S rice [45]

JERF3 Arabidopsis CaMV35S rice [43]

TSRF1 stress gene discovered

originally in Arabidopsis

CaMV35S rice [46]

OsDREB2A Arabidopsis rd29A (drought inducible) rice [48]

ZmCBF3 Arabidopsis Ubiquitin rice [72]

GhDREB Arabidopsis Zm.Ubiquitin and At.rd29A

(drought)

wheat [42]

TaDREB2;

TaDREB3

Arabidopsis double 35S and maize

RAB17

wheat

and barley

[49]

AtDREB1A/

CBF3

Arabidopsis Zm.Ubiquitin Lolium

perenne

[47]

NAC OsNAC45 reverse genetics in rice of

stress induced gene

CaMV35S rice [32]

OsNAC5 reverse genetics in rice of

stress induced gene

Zm.Ubiquitin rice [33]

OsNAC5 reverse genetics in rice of

stress induced gene

CaMV35S rice [34]

TaNAC69 reverse genetics in wheat of

stress induced gene

HvDhn8s (constitutive) or

HvDhn4s (drought-inducible)

wheat [73]

zinc finger protein OsZFP245 reverse genetics in rice of

stress induced gene

CaMV35S rice [35]

miRNA169 Sly-

miRNA169c

reverse genetics in rice of

stress induced gene

CaMV35S tomato [28]

receptor-like

kinase

OsSIK1 reverse genetics in rice of

stress induced gene

CaMV35S rice [36��]

WRKY OsWRKY11 reverse genetics in rice HSP101 promoter (heat) rice [74]

protein degradation E3 ligase OsDSG1 rice seed germination mutant RNAi rice [75]

OsDIS1 reverse genetics in rice of

stress induced gene

RNAi rice [37��]

OsSDIR1 Arabidopsis stress-

related gene

Zm.Ubiquitin rice [50]

ER chaperone BiP soyBiPD hypothesis duplicated 35S + alfalfa

mosaic virus enhancer

soybean

and

tobacco

[76]

auxin metabolism IAA amido

synthetase

Os.GH3 rice mutant CaMV35S rice [31]

cytokinin biosynthesis IPT IPT hypothesis senescence-associated

receptor kinase (SARK)

rice [77��]

Current Opinion in Biotechnology 2012, 23:243–250 www.sciencedirect.com


Table 1 (Continued )

Pathway Gene family Gene Discovery strategy Transgenic expression Crop Reference

jasmonate signaling bHLH OsbHLH148 reverse genetics in rice of

stress induced gene

Os.Cc1 (constitutive) rice [38��]

stress response,

transcript splicing

SKI-interacting

protein

OsSKIP1 reverse genetics in rice CaMV35S rice [78]

cell walls xyloglucan endo-

trans-glucosylase/

hydrolase

CaXTH3 stress-induced gene CaMV35S tomato [79]

pyrimidine nucleotide

biosynthesis

dihydroorotate

dehydrogenase

OsDHODH1 reverse genetics in rice of

stress induced gene

CaMV35S rice [39]

develop models for predicting field performance based on

greenhouse results [64]. Such modeling could improve

the success rate of greenhouse to field translation.

Based on results obtained, it may be desirable to modify

screening protocols. Screen modifications could involve

the level of drought stress used, and also the develop-

mental stage. Most drought research has been conducted

by screening and testing under severe drought con-

ditions. The types of mechanisms that can protect against

this level of stress such as reducing plant size or decreas-

ing stomatal conductance may be accompanied by

Table 2

Trangenes that have shown benefit in crops under drought stress in

Pathway Gene family Gene Discovery

osmoregulation H+-PPase AVP1 hypothesi

osmoregulation +

glycine betaine

biosynthesis

H+-Ppase + choline

dehydrogenase

BetA and

TsVP

combinat

genes wit

efficacy

ABA biosynthesis LOS5/ABA3 LOS5 stress tole

model

ABA sensing;

farnesyltransferase

farnesyltransferase BnFTA Arabidops

stress response AP2/ERF AP37 reverse g

rice of str

induced g

CBF3 stress tole

model

HARDY stress tole

model

NAC OsNAC10 reverse g

rice of str

induced g

C2H2-EAR zinc

finger protein

ZAT10 stress tole

model

MAP kinase NPK1 stress tole

model

ion transport Na+/H+ antiporter NHX1 stress tole

model

Ser/Thr kinase SOS2 stress tole

model


reduced productivity under well-watered conditions.

Identification of new gene leads by screening under

moderate rather than extreme drought may identify

genes that provide a mode-of-action more suitable for

typical agricultural environments [60��]. Most non-field

screens for drought tolerance have focused on vegetative

stages, because of the relative ease and speed of obtain-

ing data, despite the knowledge that water limitation at

the time of flowering is the most damaging to crop

productivity. Therefore, it may be productive to conduct

screening and follow-up testing using stress applied

around flowering.

field testing published from 2009 to mid-2011

strategy Transgenic expression Crop Reference

s CaMV35S cotton [80��]

ion of

h known

ZmUbiquitin maize [55]

rance in OsHVA22P (stress-

inducible) and

OsActin1

rice [53]

is RNAi with AtHPR1

promoter (drought

induced in shoot)

Canola [81]

enetics in

ess

ene

Os.Cc1 (constitutive) rice [58]


inducible) and

OsActin1 (constitutive)

rice [53]

rance in CaMV35S Trifolium

alexan-drinum

[82]

enetics in

ess

ene

RCc3 (root)

(constitutive

expression not

efficacious)

rice [54]


inducible) and

OsActin1

rice [53,83]


inducible) and

OsActin1

rice [53]

rance in Actin1 rice [53]


inducible)

rice [53,84]



ConclusionsThe value of biotechnology for improving crop yields

under stressful environments is becoming evident with

the first demonstrations of improved drought tolerance in

crops in the field (Table 2; [17�]). Many additional trans-

genes representing a variety of pathways that improve

growth under water-limiting conditions have been ident-

ified using testing in controlled environments (Table 1;

[17�]). Testing these transgenes in crop species in the

field is the next step to the development of improved

drought tolerance with agricultural significance.

The pace of development of additional drought tolerant

traits may be advanced by combining efforts of academia

and industry. For example, infrastructure established

within industry for field testing across multiple environ-

ments could be applied to help demonstrate the trans-

lation between laboratory studies and the field for the

large numbers of transgenes identified by academic

institutions. Academic researchers may be in the best

position to conduct more detailed studies on molecular or

physiological mechanisms for specific gene pathways that

could be used to help predict field performance.

It is likely that multiple mechanisms of drought tolerance

will be needed to provide robust tolerance that can protect

against the variety of drought stress types that may be

encountered across a range of geographies. Drought toler-

ant crops will ultimately be produced by combining the

products of advanced farming practices and breeding with

traits developed through biotechnology [65].

AcknowledgementsWe thank Carolyn O’Reilly and Laura Grapes for help with backgroundresearch, and Susanne Kjemtrup and Matt Tanzer for photographs used inthe figure.

References and recommended readingPapers of particular interest, published within the period of review,have been highlighted as:

� of special interest

�� of outstanding interest

1. Godfray HCJ, Beddington JR, Crute IR, Haddad L, Lawrence D,Muir JF, Pretty J, Robinson S, Thomas SM, Toulmin C: Foodsecurity: the challenge of feeding 9 billion people. Science2010, 327:812-818.

2. Lobell DB, Burke MB, Tebaldi C, Mastrandrea MD, Falcon WP,Naylor RL: Prioritizing climate change adaptation needs forfood security in 2030. Science 2008, 319:607-610.

3. Tollenaar M, Lee EA: Yield potential, yield stability and stresstolerance in maize. Field Crops Research 2002, 75:161-169.

4. Boyer JS: Plant productivity and environment. Science 1982,218:443-448.

5.�

Yoo CY, Pence HE, Hasegawa PM, Mickelbart MV: Regulation oftranspiration to improve crop water use. Critical Reviews inPlant Sciences 2009, 28:410-431.

A thoughtful review of regulation of stomatal conductance to improvewater use efficiency. Genetic evidence supporting optimization of wateruse efficiency is discussed. A review of genes that can modulate tran-spiration is included.


6. Passioura J: The drought environment: physical, biological andagricultural perspectives. Journal of Experimental Botany 2007,58:113-117.

7. Borlaug NE: Ending world hunger. The promise ofbiotechnology and the threat of antiscience zealotry. PlantPhysiology 2000, 124:487-490.

8.��

Raymond Park J, McFarlane I, Hartley Phipps R, Ceddia G: Therole of transgenic crops in sustainable development. PlantBiotechnology Journal 2011, 9:2-21.

An interesting review of the effect of transgenic crops globally on econ-omy, environment and society.

9. Neumann PM: Coping mechanisms for crop plants in drought-prone environments. Annals of Botany 2008, 101:901-907.

10.�

Lopes MS, Araus JL, van Heerden PDR, Foyer CH: Enhancingdrought tolerance in C4 crops. Journal of ExperimentalBotany 2011.

A nice review that describes various approaches to modification of C4plants for increased drought tolerance, covering both above-ground andbelow-ground strategies.

11. Gowda VRP, Henry A, Yamauchi A, Shashidhar HE, Serraj R: Rootbiology and genetic improvement for drought avoidance inrice. Field Crops Research 2011, 122:1-13.

12. Umezawa T, Fujita M, Fujita Y, Yamaguchi-Shinozaki K,Shinozaki K: Engineering drought tolerance in plants:discovering and tailoring genes to unlock the future. CurrentOpinion in Biotechnology 2006, 17:113-122.

13. Hubbard KE, Nishimura N, Hitomi K, Getzoff ED, Schroeder JI:Early abscisic acid signal transduction mechanisms: newlydiscovered components and newly emerging questions.Genes & Development 2010, 24:1695-1708.

14. C akir R: Effect of water stress at different development stageson vegetative and reproductive growth of corn. Field CropsResearch 2004, 89:1-16.

15. Claassen MM, Shaw RH: Water deficit effects on corn. 2. Graincomponents. Agronomy Journal 1970, 62:652-655.

16. Tollefson J: Drought-tolerant maize gets US debut. Nature 2011,469:144.

17.�

Yang S, Vanderbeld B, Wan J, Huang Y: Narrowing down thetargets: towards successful genetic engineering of drought-tolerant crops. Molecular Plant 2010, 3:469-490.

Excellent detailed overview of biotech approaches to improving droughttolerance in crops.

18. Hirayama T, Shinozaki K: Research on plant abiotic stressresponses in the post-genome era: past, present and future.The Plant Journal 2010, 61:1041-1052.

19. Nakashima K, Ito Y, Yamaguchi-Shinozaki K: Transcriptionalregulatory networks in response to abiotic stresses inArabidopsis and grasses. Plant Physiology 2009, 149:88-95.

20.��

Joshi-Saha A, Valon C, Leung J: Abscisic acid signal off theSTARTing block. Molecular Plant 2011, 4:562-580.

A thorough, yet succinct, description of current understanding of ABAsignaling including perception, signaling, control of gene expression, andpost-transcriptional regulation.

21. Kline KG, Sussman MR, Jones AM: Abscisic acid receptors.Plant Physiology 2010, 154:479-482.

22. Century K, Reuber TL, Ratcliffe OJ: Regulating the regulators: thefuture prospects for transcription-factor-based agriculturalbiotechnology products. Plant Physiology 2008, 147:20-29.

23. Xu Z-S, Chen M, Li L-C, Ma Y-Z: Functions and application ofthe AP2/ERF transcription factor family in crop improvement.Journal of Integrative Plant Biology 2011, 53:570-585.

24. Covarrubias AA, Reyes JL: Post-transcriptional gene regulationof salinity and drought responses by plant microRNAs. Plant,Cell & Environment 2010, 33:481-489.

25. Wang T, Chen L, Zhao M, Tian Q, Zhang W-H: Identification ofdrought-responsive microRNAs in Medicago truncatula bygenome-wide high-throughput sequencing. BMC Genomics2011, 12:367.



26. Zhang L, Chia J-M, Kumari S, Stein JC, Liu Z, Narechania A,Maher CA, Guill K, McMullen MD, Ware D: A genome-widecharacterization of MicroRNA genes in maize. PLoS Genetics2009, 5:e1000716.

27. Zhou L, Liu Y, Liu Z, Kong D, Duan M, Luo L: Genome-wideidentification and analysis of drought-responsive microRNAsin Oryza sativa. Journal of Experimental Botany 2010,61:4157-4168.

28. Zhang X, Zou Z, Gong P, Zhang J, Ziaf K, Li H, Xiao F, Ye Z: Over-expression of microRNA169 confers enhanced droughttolerance to tomato. Biotechnology Letters 2011,33:403-409.

29. Du H, Wang N, Cui F, Li X, Xiao J, Xiong L: Characterization of theb-carotene hydroxylase gene DSM2 conferring drought andoxidative stress resistance by increasing xanthophylls andabscisic acid synthesis in rice. Plant Physiology 2010,154:1304-1318.

30.��

Huang X-Y, Chao D-Y, Gao JP, Zhu M-Z, Shi M, Lin HX: Apreviously unknown zinc finger protein, DST, regulatesdrought and salt tolerance in rice via stomatal aperturecontrol. Genes & Development 2009, 23:1805-1817.

The DST gene was cloned using a rice mutant that had improved droughttolerance. DST negatively regulates stomatal closure by modulation ofgenes related to peroxide homeostasis, and also regulates stomataldensity and leaf width.

31. Zhang S-W, Li C-H, Cao J, Zhang Y-C, Zhang S-Q, Xia Y-F, Sun D-Y, Sun Y: Altered architecture and enhanced drought tolerancein rice via the down-regulation of indole-3-acetic acid byTLD1/OsGH3.13 activation. Plant Physiology (Rockville) 2009,151:1889-1901.

32. Zheng X, Chen B, Lu G, Han B: Overexpression of a NACtranscription factor enhances rice drought and salt tolerance.Biochemical and Biophysical Research Communications 2009,379:985-989.

33. Takasaki H, Maruyama K, Kidokoro S, Ito Y, Fujita Y, Shinozaki K,Yamaguchi-Shinozaki K, Nakashima K: The abiotic stress-responsive NAC-type transcription factor OsNAC5 regulatesstress-inducible genes and stress tolerance in rice. MolecularGenetics and Genomics 2010, 284:173-183.

34. Song S-Y, Chen Y, Chen J, Dai X-Y, Zhang W-H: Physiologicalmechanisms underlying OsNAC5-dependent tolerance of riceplants to abiotic stress. Planta 2011, 234:331-345.

35. Huang J, Sun S-J, Xu D-Q, Yang X, Bao Y-M, Wang Z-F, Tang H-J,Zhang H: Increased tolerance of rice to cold, drought andoxidative stresses mediated by the overexpression of agene that encodes the zinc finger protein ZFP245.Biochemical and Biophysical Research Communications 2009,389:556-561.

36.��

Ouyang SQ, Liu YF, Liu P, Lei G, He SJ, Ma B, Zhang WK,Zhang JS, Chen SY: Receptor-like kinase OsSIK1 improvesdrought and salt stress tolerance in rice (Oryza sativa) plants.Plant Journal 2010, 62:316-329.

Overexpression of OsSIK1 produced improved drought and salt toler-ance in rice. Lines with reduced expression of OsSIK1 (RNAi and mutants)were more sensitive to drought and salt stress. Overexpression of OsSIK1resulted in increased antioxidant activity and reduced stomatal density.

37.��

Ning Y, Jantasuriyarat C, Zhao Q, Zhang H, Chen S, Liu J, Liu L,Tang S, Park CH, Wang X et al.: The SINA E3 ligase OsDIS1negatively regulates drought response in rice. Plant Physiology2011, 157:242-255.

Overexpression of OsDIS1 reduced drought tolerance of rice, but genesuppression by RNAi improved drought tolerance. This E3 ligase, which isinduced by drought stress, appears to play a negative role in droughtstress response by both transcriptional and post-transcriptional regula-tion of stress-related genes.

38.��

Seo JS, Joo J, Kim MJ, Kim YK, Nahm BH, Song SI, Cheong JJ,Lee JS, Kim JK, Do Choi Y: OsbHLH148, a basic helix-loop-helixprotein, interacts with OsJAZ proteins in a jasmonatesignaling pathway leading to drought tolerance in rice. PlantJournal 2011, 65:907-921.

A nice example of the use of reverse genetics in rice to show the role of astress-induced and jasmonate-induced gene in drought response.


39. Liu W-Y, Wang M-M, Huang J, Tang H-J, Lan H-X, Zhang H-S: TheOsDHODH1 gene is involved in salt and drought tolerance inrice. Journal of Integrative Plant Biology 2009, 51:825-833.

40. Lu G, Gao C, Zheng X, Han B: Identification of OsbZIP72 as apositive regulator of ABA response and drought tolerance inrice. Planta (Berlin) 2009, 229:605-615.

41. Gao SQ, Chen M, Xu ZS, Zhao CP, Li LC, Xu HJ, Tang YM, Zhao X,Ma YZ: The soybean GmbZIP1 transcription factor enhancesmultiple abiotic stress tolerances in transgenic plants. PlantMolecular Biology 2011, 75:537-553.

42. Gao S-Q, Chen M, Xia L-Q, Xiu H-J, Xu Z-S, Li L-C, Zhao C-P,Cheng X-G, Ma Y-Z: A cotton (Gossypium hirsutum) DRE-binding transcription factor gene, GhDREB, confers enhancedtolerance to drought, high salt, and freezing stresses intransgenic wheat. Plant Cell Reports 2009, 28:301-311.

43. Zhang H, Liu W, Wan L, Li F, Dai L, Li D, Zhang Z, Huang R:Functional analyses of ethylene response factor JERF3 withthe aim of improving tolerance to drought and osmotic stressin transgenic rice. Transgenic Research 2010, 19:809-818.

44. Zhang S, Li N, Gao F, Yang A, Zhang J: Over-expression ofTsCBF1 gene confers improved drought tolerance intransgenic maize. Molecular Breeding 2010, 26:455-465.

45. Zhang Z, Li F, Li D, Zhang H, Huang R: Expression of ethyleneresponse factor JERF1 in rice improves tolerance to drought.Planta (Berlin) 2010, 232:765-774.

46. Quan R, Hu S, Zhang Z, Zhang H, Zhang Z, Huang R:Overexpression of an ERF transcription factor TSRF1improves rice drought tolerance. Plant Biotechnology Journal2010, 8:476-488.

47. Li X, Cheng X, Liu J, Zeng H, Han L, Tang W: Heterologousexpression of the Arabidopsis DREB1A/CBF3 gene enhancesdrought and freezing tolerance in transgenic Lolium perenneplants. Plant Biotechnology Reports 2011, 5:61-69.

48. Mallikarjuna G, Mallikarjuna K, Reddy M, Kaul T: Expression ofOsDREB2A transcription factor confers enhanceddehydration and salt stress tolerance in rice (Oryza sativa L.).Biotechnology Letters 2011, 33:1689-1697.

49. Morran S, Eini O, Pyvovarenko T, Parent B, Singh R, Ismagul A,Eliby S, Shirley N, Langridge P, Lopato S: Improvement of stresstolerance of wheat and barley by modulation of expression ofDREB/CBF factors. Plant Biotechnology Journal 2011,9:230-249.

50. Gao T, Wu Y, Zhang Y, Liu L, Ning Y, Wang D, Tong H, Chen S,Chu C, Xie Q: OsSDIR1 overexpression greatly improvesdrought tolerance in transgenic rice. Plant Molecular Biology2011, 76:145-156.

51. Lv S-L, Lian L-J, Tao P-L, Li Z-X, Zhang K-W, Zhang J-R:Overexpression of Thellungiella halophila H+-PPase (TsVP) incotton enhances drought stress resistance of plants. Planta(Berlin) 2009, 229:899-910.

52. Wang G-P, Hui Z, Li F, Zhao M-R, Zhang J, Wang W:Improvement of heat and drought photosynthetic tolerance inwheat by overaccumulation of glycinebetaine. PlantBiotechnology Reports 2010, 4:213-222.

53. Xiao B-Z, Chen X, Xiang C-B, Tang N, Zhang Q-F, Xiong L-Z:Evaluation of seven function-known candidate genes for theireffects on improving drought resistance of transgenic riceunder field conditions. Molecular Plant 2009, 2:73-83.

54. Jeong JS, Kim YS, Baek KH, Jung H, Ha SH, Do Choi Y, Kim M,Reuzeau C, Kim JK: Root-specific expression of OsNAC10improves drought tolerance and grain yield in rice under fielddrought conditions. Plant Physiology 2010, 153:185-197.

55. Wei A, He C, Li B, Li N, Zhang J: The pyramid of transgenes TsVPand BetA effectively enhances the drought tolerance of maizeplants. Plant Biotechnology Journal 2011, 9:216-229.

56. Fedoroff NV, Battisti DS, Beachy RN, Cooper PJM, Fischhoff DA,Hodges CN, Knauf VC, Lobell D, Mazur BJ, Molden D et al.:Radically rethinking agriculture for the 21st century. Science2010, 327:833-834.



57. Castiglioni P, Warner D, Bensen RJ, Anstrom DC, Harrison J,Stoecker M, Abad M, Kumar G, Salvador S, D’Ordine R et al.:Bacterial RNA chaperones confer abiotic stress tolerance inplants and improved grain yield in maize under water-limitedconditions. Plant Physiology 2008, 147:446-455.

58. Oh S-J, Kim YS, Kwon C-W, Park HK, Jeong JS, Kim J-K:Overexpression of the transcription factor AP37 in riceimproves grain yield under drought conditions. PlantPhysiology (Rockville) 2009, 150:1368-1379.

59. Blum A: Drought resistance – is it really a complex trait?Functional Plant Biology 2011, 38:753-757.

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Skirycz A, Vandenbroucke K, Clauw P, Maleux K, De Meyer B,Dhondt S, Pucci A, Gonzalez N, Hoeberichts F, Tognetti VB et al.:Survival and growth of Arabidopsis plants given limited waterare not equal. Nature Biotechnology 2011, 29:212-214.

A must-read perspective of strategies for identification of genes useful forengineering agriculturally relevant drought tolerance.

61. Berger B, Parent B, Tester M: High-throughput shoot imaging tostudy drought responses. Journal of Experimental Botany 2010,61:3519-3528.

62. Reuzeau C, Pen J, Frankard V, Wolf Jd, Peerbolte R, Broekaert W,Camp Wv: TraitMill: a discovery engine for identifyingyield-enhancement genes in cereals. Plant Gene and Trait 2010,1: doi: 10.5376/pgt.2010.5301.0001.

63. Zhu J, Ingram PA, Benfey PN, Elich T: From lab to field, newapproaches to phenotyping root system architecture. CurrentOpinion in Plant Biology 2011, 14:310-317.

64. Tardieu F, Tuberosa R: Dissection and modelling of abioticstress tolerance in plants. Current Opinion in Plant Biology 2010,13:206-212.

65. Varshney RK, Bansal KC, Aggarwal PK, Datta SK, Craufurd PQ:Agricultural biotechnology for crop improvement in a variableclimate: hope or hype? Trends in Plant Science 2011, 16:363-371.

66. Bao A-K, Wang S-M, Wu G-Q, Xi J-J, Zhang J-L, Wang C-M:Overexpression of the Arabidopsis H+-PPase enhancedresistance to salt and drought stress in transgenic alfalfa(Medicago sativa L.). Plant Science 2009, 176:232-240.

67. He CM, Zhang WW, Gao QA, Yang AF, Hu XR, Zhang JR:Enhancement of drought resistance and biomass byincreasing the amount of glycine betaine in wheat seedlings.Euphytica 2011, 177:151-167.

68. Ji W, Zhu Y, Li Y, Yang L, Zhao X, Cai H, Bai X: Over-expression ofa glutathione S-transferase gene, GsGST, from wild soybean(Glycine soja) enhances drought and salt tolerance intransgenic tobacco. Biotechnology Letters 2010, 32:1173-1179.

69. Hsieh T-H, Li C-W, Su R-C, Cheng C-P, Sanjaya S, Tsai Y-C,Chan M-T: A tomato bZIP transcription factor, SlAREB, isinvolved in water deficit and salt stress response. Planta 2010,231:1459-1473.

70. Manavalan LP, Chen X, Clarke J, Salmeron J, Nguyen HT: RNAi-mediated disruption of squalene synthase improves droughttolerance and yield in rice. Journal of Experimental Botany 2011.doi:10.1093/jxb/err258.

71. Zhang L, Xiao S, Li W, Feng W, Li J, Wu Z, Gao X, Liu F, Shao M:Overexpression of a Harpin-encoding gene hrf1 in riceenhances drought tolerance. Journal of Experimental Botany2011, 62:4229-4238.

72. Xu M, Li L, Fan Y, Wan J, Wang L: ZmCBF3 overexpressionimproves tolerance to abiotic stress in transgenic rice (Oryzasativa) without yield penalty. Plant Cell Reports 2011:1-9.

73. Xue G-P, Way HM, Richardson T, Drenth J, Joyce PA, McIntyre CL:Overexpression of TaNAC69 leads to enhanced transcript


levels of stress up-regulated genes and dehydration tolerancein bread wheat. Molecular Plant 2011 doi: 10.1093/mp/ssr013.

74. Wu X, Shiroto Y, Kishitani S, Ito Y, Toriyama K: Enhanced heatand drought tolerance in transgenic rice seedlingsoverexpressing OsWRKY11 under the control of HSP101promoter. Plant Cell Reports 2009, 28:21-30.

75. Park G-G, Park J-J, Yoon J, Yu S-N, An G: A RING finger E3ligase gene, Oryza sativa Delayed Seed Germination 1(OsDSG1), controls seed germination and stress responses inrice. Plant Molecular Biology 2010, 74:467-478.

76. Valente MAS, Faria JAQA, Soares-Ramos JRL, Reis PAB,Pinheiro GL, Piovesan ND, Morais AT, Menezes CC, Cano MAO,Fietto LG et al.: The ER luminal binding protein (BiP) mediatesan increase in drought tolerance in soybean and delaysdrought-induced leaf senescence in soybean and tobacco.Journal of Experimental Botany 2009, 60:533-546.

77.��

Peleg Z, Reguera M, Tumimbang E, Walia H, Blumwald E:Cytokinin-mediated source/sink modifications improvedrought tolerance and increase grain yield in rice under water-stress. Plant Biotechnology Journal 2011, 9:747-758.

This work shows that increased production of cytokinins using a senes-cence-induced promoter can improve drought tolerance in rice. In-depthcharacterization of the effects of the construct is provided, leading to ahypothesis that the construct produces a stronger sink capacity duringdrought stress.

78. Hou X, Xie K, Yao J, Qi Z, Xiong L: A homolog of human ski-interacting protein in rice positively regulates cell viabilityand stress tolerance. In Proceedings of the NationalAcademy of Sciences of the United States of America 2009,106:6410-6415.

79. Choi JY, Seo YS, Kim SJ, Kim WT, Shin JS: Constitutiveexpression of CaXTH3, a hot pepper xyloglucanendotransglucosylase/hydrolase, enhanced tolerance to saltand drought stresses without phenotypic defects in tomatoplants (Solanum lycopersicum cv. Dotaerang). Plant CellReports 2011, 30:867-877.

80.��

Pasapula V, Shen G, Kuppu S, Paez-Valencia J, Mendoza M,Hou P, Chen J, Qiu X, Zhu L, Zhang X et al.: Expression of anArabidopsis vacuolar H+-pyrophosphatase gene (AVP1) incotton improves drought- and salt tolerance and increasesfibre yield in the field conditions. Plant Biotechnology Journal2011, 9:88-99.

Increasing expression of a vacuolar membrane-bound H+ pump hasbeen shown to provide increased salt-tolerance and drought-tolerance inseveral species, including cotton, as described in this paper.

81. Wang Y, Beaith M, Chalifoux M, Ying J, Uchacz T, Sarvas C,Griffiths R, Kuzma M, Wan J, Huang Y: Shoot-specific down-regulation of protein farnesyltransferase (alpha-subunit) foryield protection against drought in canola. Molecular Plant2009, 2:191-200.

82. Abogadallah G, Nada R, Malinowski R, Quick P: Overexpressionof HARDY, an AP2/ERF gene from Arabidopsis, improvesdrought and salt tolerance by reducing transpiration andsodium uptake in transgenic Trifolium alexandrinum L. Planta2011, 233:1265-1276.

83. Mittler R, Kim Y, Song L, Coutu J, Coutu A, Ciftci-Yilmaz S, Lee H,Stevenson B, Zhu J-K: Gain- and loss-of-function mutations inZat10 enhance the tolerance of plants to abiotic stress. FEBSLetters 2006, 580:6537-6542.

84. Batelli G, Verslues PE, Agius F, Qiu Q, Fujii H, Pan S,Schumaker KS, Grillo S, Zhu J-K: SOS2 promotes salt tolerancein part by interacting with the vacuolar H+-ATPase andupregulating its transport activity. Molecular and CellularBiology 2007, 27:7781-7790.


http://dx.doi.org/10.5376/pgt.2010.5301.0001

http://dx.doi.org/10.1093/mp/ssr013

drought tolerance through biotechnology: improving translation from the laboratory to farmers’...

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